In a single-ended signaling system, a transmitter generates a single voltage signal which is transmitted to a receiver, wherein the voltage signal is subsequently compared against a fixed reference voltage which is typically generated on the receiver or transmitted from transmitter to receiver. Note that the quality of this reference voltage can directly affect the voltage margin (e.g., the swing at the receiver input) of the receiver, which has direct impact on the timing margin and thus the data rate of the single-ended signaling system. Hence, for high-speed, high-performance operations in a single-ended signaling system, it is necessary to generate a high-quality reference voltage on the receiver, which involves producing an accurate DC level and a proper AC noise characteristic.
However, generating a high-quality reference voltage with both an accurate DC level and a proper AC noise characteristic can be challenging. From the “accurate DC level” aspect, the accuracy in the DC level of the reference voltage can suffer from DC offsets arising from circuit mismatches between the transmitter and the receiver, as well as intrinsic DC offsets within the amplifier and sampling circuits on the receiver. From the “proper AC noise characteristic” aspect, the challenge lies in that the reference voltage has to include an AC noise spectrum that is capable of offsetting a corresponding AC noise spectrum in the received signal. More specifically, the reference voltage can be coupled to both a positive node (referred to as “Vdd”) and a ground node (referred to as “Vss”) of a power supply on the receiver, wherein Vdd and Vss may have different noise spectrum. Moreover, the single-ended signal generated on the transmitter can also be coupled to noises in both Vdd and Vss of a power supply on the transmitter. Because the noise spectrum in the Vdd on the transmitter may be different from the noise spectrum in the Vdd on the receiver, and the noise spectrum in the Vss on the transmitter may be different from the noise spectrum in the Vss on the receiver, it is extremely difficult to accurately track the AC noises in the single-ended signal using the intrinsic AC noises in the reference voltage.